1. TECHNICAL FIELD
The present invention relates to magnetoresistive transducers. More particularly, the present invention relates to improvements in conductor configurations for magnetoresistive transducers.
2. DESCRIPTION OF THE PRIOR ART
Continuing advances in magnetic media technology allow increasing data storage densities. One active area of development is that of reading transducers of high output. As such transducers are made smaller, data densities are increased. Magnetoresistive (MR) thin film technology has provided a particularly promising area of inquiry with regard to producing smaller reading transducers. In such technology, conductive thin films are formed on a substrate using techniques analogous to those of the semiconductor arts.
The MR stripe or element in a single stripe MR transducer (or the two MR stripes or elements is a dual stripe MR transducer, such as is described in U.S. Pat. No. 3,860,965, issued to Voegeli), must be long with respect to a magnetic medium track width. In this way, the transducer presents a stable domain state. Various configurations have been proposed for contacting the MR stripe to provide a source of current to the stripe and to sense flux (i.e. data) with the MR stripe arrangement.
One such conductor arrangement from prior art, shown in FIGS. 1a and 1b, provides two conductors 12,14 for contacting each MR stripe 16. In the Fig. current directions are indicated by the designation `i`, magnetic field directions by the designation `H`, and magnetization directions by the designation `M`. These conventions shall be applied throughout the present application.
The arrangement shown, referred to as a conductors-over arrangement because the conductors are arranged above an MR stripe, is used in barber-pole biased MR heads. The conductors-over arrangement is prone to shorting either to the transducer shields (not shown) or to the other MR stripe (in a dual stripe MR transducer). Such shorting is due to conductor smearing during the lapping process used to form the transducer air bearing surface, or as a consequence of encountering an asperity on the surface of a disk in an operating disk drive.
The length of the conductor along the transducer air bearing surface is of critical importance. The length of the conductor in FIG. 1a can be as much as 400 .mu.m and as little as 40 .mu.m. The longer this dimension, the more likely a short can occur between transducer shields (not shown) and the MR conductors, or between the two MR conductors in a dual stripe transducer, as a consequence of lapping the transducer air bearing surface, or as a consequence of contacting disk asperities as previously described.
Another arrangement discussed in the prior art, shown in FIGS. 2a and 2b, is referred to, appropriately, as a tip arrangement. A tip transducer includes conductors 21,22 arranged to carry current to and from an MR element 26. It is generally acknowledged that this arrangement was developed by International Business Machines of Armonk, N.Y. It has been the experience of those working with transducers having a tip arrangement that such configuration leads to unequal track edge response, in part because of the way magnetic fields `H` are imposed in different directions at the conductor (track edge) edges due to the electrical current `i`.
In FIG. 2a, the directions of the magnetic fields `H` induced by the currents `i` are not equivalent, even if the current does not bend as assumed at the track edges. Thus, the magnetization `M` is rotated unequally at the track edges. Accordingly, different responses occur at the track edges and, as a result, track profiles become asymmetric.
The length of the MR element (or elements in a dual stripe transducer configuration) must also be significantly larger than the track width to achieve high track density reproduction with a single domain MR transducer. One practice is to place the MR sensor portion of an MR transducer between two magnetic shields to obtain high resolution along the track. In an MR read element, the active area is defined as the area in which sense current flows in the MR element and typically results from the placement of the conductor leads which carry current to and from the MR element. The leads and MR element in combination constitute a single turn coil which gives rise to an undesirable inductive response to recorded information. The magnitude of this response is determined by the number of tracks over which such coil extends.
Thus, the state of MR transducer art presents a technology that suffers from various problems associated with conductor arrangement, including low yields due to shorting, poor symmetry in track profiles due to a lack if uniform fields at the track edges, and inductive pickup which results in intertrack interference.